1. Field of the Invention
The present invention relates to a method for contour recognition of totally or partly transparent objects, e.g. bottles made of glass or plastic, and being advanced through an illumination and detector station and being illuminated there on at least one portion of the circumferencial area.
2. Description of Related Art
From U.S. Pat. Nos. 3,955,197 and 4,055,834 it is known to advance a bottle continuously through an illuminating and detector station, light being projected from one side of a conveyor toward the bottle to form a shadow image or part of a shadow image of the bottle on a light detector means. It is, thus, common to said devices that the light is projected toward the bottle, and if said bottle is made of glass or plastic refraction phenomena may occur to cause possible false signals in the detector. Even though such refraction phenomena are relatively small, in particular with the device described in U.S. Pat. No. 4,055,834 it is, nevertheless, desirable to obtain an image of the bottle or liquid container that is as true as possible.
Furthermore, it is known from U.S. Pat. No. 3,529,169 to keep a bottle immovable in the direction of conveyance while its contour is recognized in the illumination and detector station. U.S. Pat. No. 3,529,169 also describes means to rotate the object while it remains at said station. However, it has been desirable for some time to simplify both the illuminating and the detector portion of such a station.